Closure Compiler is a JavaScript optimizing compiler. It parses your JavaScript, analyzes it, removes dead code and rewrites and minimizes what's left. It also checks syntax, variable references, and types, and warns about common JavaScript pitfalls. It is used in many of Google's JavaScript apps, including Gmail, Google Web Search, Google Maps, and Google Docs.

Wro4j Extensions

Zipper is a full-featured asset packaging plugin for Maven that provides JavaScript lint lint checking, Closure Compiler and YUI Compressor support, CSS and JavaScript concatenation, and up-front gzipping.